1. Field of the Invention
The present invention relates to a light source apparatus and a projection type display apparatus.
Priority is claimed on Japanese Patent Application No. 2004-5411, filed Jan. 13, 2004, Japanese Patent Application No. 2004-7903, filed Jan. 15, 2004, and Japanese Patent Application No. 2004-330534, filed Nov. 15, 2004 the contents of which are incorporated herein by reference.
2. Description of Related Art
Projectors (i.e., projection type display apparatuses) have in recent years achieved reductions in size, improvements in luminance, longer life spans, and reductions in cost. For example, as far as size reductions are concerned, the size of liquid crystal panels (i.e., optical modulators) has been reduced from 1.3 inches diagonally to 0.5 inches so that a size reduction of more than one sixth (as a surface ratio) is achieved.
It has also been proposed that a reduction in size can be achieved by using a light emitting diode (i.e., LED), which is a solid state light source, as the light source of a projector.
LED light sources are small in size while including a power source, and have merit as the light source of a projector in that they allow instantaneous ON and OFF and have broad color reproducibility and long life spans. In addition, because they contain no harmful substances such as mercury, they are preferable from the viewpoint of environmental protection.
However, because the brightness of an LED light source is insufficient as the light source of a projector, for an LED light source to be used as the light source of a projector, it has been necessary to ensure at least the level of brightness of a discharge type of light source lamp (i.e., it has been necessary to raise the luminance and lower the etendue). Here, the term “etendue” refers to a numerical value that indicates a spatial expanse in which luminous flux that can be effectively used is present expressed as the product of a surface area and a solid angle. Moreover, the etendue is optically preserved. As described above, because a reduction in the size of liquid crystal panels has been achieved and the etendue of liquid crystal panels has been reduced, it is also necessary to reduce the etendue of the light source comparably or smaller.
However, as the level of brightness of LED light sources has increased, the heat generated from LED light sources has also further increased. However, if the temperature of an LED light source rises, the light emission efficiency thereof deteriorates, so that some type of countermeasure against heat has been required. In the forced air-cooling system using a fan that is generally employed, the cooling effect is insufficient and the noise from the fan has created problems. For this reason, methods for forcibly cooling an LED light source using a liquid have been proposed. From a liquid cooling method, an effect of nullifying the noise generated in the forced air-cooling system is also anticipated (for example, in Japanese Unexamined Patent Application, First Publication Nos. H06-005923 and H07-099372).
In the LED light source disclosed in Japanese Unexamined Patent Application, First Publication No. H06-005923, by circulating a coolant such as liquid nitrogen or the like around the LED, the LED and the coolant are placed in direct contact with each other so as to achieve forced cooling. However, because the structure of the LED light source is complex such as an insulating casing being necessary and the like, the manufacture thereof is not practical. Therefore, the problem arises that it is difficult to ensure at the least the brightness level of a discharge type light source lamp.
In the LED light source disclosed in Japanese Unexamined Patent Application, First Publication No. H07-099372, the periphery of an LED chip (i.e., the light emitting chip) is filled with an insulating inert liquid so as to cool the LED chip. However; a device for actively cooling the insulating inert liquid is not provided, so that the cooling effect is low and it is difficult to cool an LED chip for an extended period of time. Consequently, the problem arises that it is difficult to ensure at the least the brightness level of a discharge type light source lamp.